The disclosure is related to methods and devices for providing data transmission between video source and sink hardware. The present disclosure is related more specifically to methods and devices for providing high speed data transmission of non-display related data along with video data over a unified cable.
Multi-stream transport (MST) architecture, such as DisplayPort™, provides an AC-coupled voltage-differential interface. The interface consists of three different channels: a main link, an AUX channel, and a hot plug detect (HPD). The main link features one, two or four scalable data pairs (or lanes) that can be operated at different rates (Gbit/sec). The main link lanes and the AUX channel are differential signals formed from twisted pairs of lines and the HPD is a single wire. MST utilizes a link service within a source device to discover, configure and maintain a link with devices it connects to. The link service configures the link through as link training. Link training is a process where the correct number of lanes are enabled and the signals are tuned at the required link rate via a handshake between the MST transmitter (graphics output) and the MST receiver (repeater, hub or display) over the AUX channel.
MST control symbols are used for data such as video into display frame information. For each scan line, for example, a blanking start (BS) control symbol is sent that indicates, for example, where the last video data transfer unit ends. Data is sent as transfer units (micropackets). Blanking end (BE) information indicates where the first video data transfer unit begins for a display line, fill start (FS) information indicates where dummy data symbols start in each transfer unit and fill end and other symbols are also utilized. Control data is also sent as part of every frame, sent in a given lane and follows the blanking start (BS) information. Such blanking start information as noted above, indicates, for example, the end of a scan line. Control data includes, for example, information regarding video and audio and timing information, such as display frame, field or scan line information and related timing information. As such, redundant control symbols and control data is sent over multiple lanes. The last symbol time for a line of pixel data is followed by the control symbol BS which is inserted on all lanes of the link.
Technology has been developed under the name Thunderbolt™ which combines PCI Express and DisplayPort™ into a serial data interface. Thunderbolt provides bi-directional data communication that requires an active cable, i.e. copper cables that use silicon chips in the connectors to boost the performance of the cable. The cable has high speed differential pairs of wires for data flow in each direction along with wiring for management purposes. The active nature of the cable and the hardware controllers to handle the data cause the Thunderbolt solution to be relatively expensive. There also exists technology which modifies the physical layer of the AUX channel to permit high-speed bi-directional data transmission. This allows for bi-directional transmission speeds similar to that of the main link, but as mention requires a physical modification to the DisplayPort™ architecture which can be costly.